Grinding of solids



United States Patent 6 3,295,766 GRINDING F SOLIDS Elmer C. Tveter, Concord, Calif., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed Sept. 8, 1964, Ser. No. 395,034 5 Claims. (Cl. 241-15) This invention relates to the grinding of mineral ores and more particularly is concerned with a novel method of grinding such materials in the presence of a liquid to effect enhanced liberation of valuable constituents therefrom. i

It is a principal object of the present invention to provide a novel process wherein maximum mineral value liberation from a given mineral ore is realized with a minimum of particle size reduction.

This and other objects and advantages readily will be apparent from the detailed description presented hereinafter.

In accordance with the present invention, a solid ore material, e.g., multicornponent ore particles having interlocked grains of different mineral species, is introduced to suitable grinding means, such as a mill. A liquid having a specific gravity at operational temperature greater than 1.0 of the type disclosed herein is also introduced to the grinding means and this mixture then ground. Solid ore material to be ground may be slurried with the liquid prior to grinding, or the liquid may be added to the solid material in the grinding means.

The actual grinding time to be employed in order to meet product specification will vary from ore to ore and readily can be determined by one skilled in the art. Usually grinding times are determined so as to provide a maximum amount of mineral value liberation with a minimum amount of ore particle size reduction. Unexpectedly, it has been in the present novel process that mineral values are liberated as relatively large particles without excessive grinding.

Operable amounts of liquid to be used with the solid material during grinding should be sufiicient to provide a zone distinct from the zone in which grinding takes place within the grinding means. Usually, process liquid and solid material are introduced to the grinding means as a mixture containing from about 5 to about 60 percent by weight solid material. Preferably, from about 5 to about 40 percent solid material, the balance being the liquid, is present in the grinding means.

Liquids suitable for use in the present method have a specific gravity, at operational temperatures, greater than 1.0. Desirably, process liquids employed in the present invention have a specific gravity greater than 1.0 and up to about the specific gravity of the densest component of the solid material to be ground. Preferably, the process liquid employed in the present invention has a specific gravity of from about 1.4 to about 3.0 and intermediate the specific gravity of at least two of the solid materials to be ground at the operational temperature.

Liquids ordinarily employed in the present method are organic liquid compounds or mixtures of such compounds substantially non-reactive with the material to be ground, not detrimentally degraded by process conditions and having the requisite specific gravity. When a plurality of such compounds is employed, the compounds should be mutually miscible.

Preferred liquid compounds for use in the process of ice the present invention are halogenated hydrocarbons, and mixtures thereof, which contain from one to two carbon atoms and from two to six halogens atoms. Representative examples of such halogenated hydrocarbons and their respective specific gravities, useful in the present process are: carbon tetrachloride (1.959); perchloroethylene (1.619); methylene bromide (2.485); methylene chlorobromide (1.930); dibromo chloro methane (2.44); tribromo fluoro methane (2.8); bromo 'trichloro methane (2.0); bromo iodo methane (2.93); dibromo dichloro methane (2.41); bromo dichloro methane (1.97); 1,2- dibromo ethane (2.17); 1,'1,2,2-tetrafluoro l,2-diiodo ethane (2.63); 1,1-dibromo 2,2-difluoro ethane (2.31); 1,2-dibromo 1,1,2-trichloro ethane (2.27); 1,2-dibromo 2-ch1oro 1,1,2-trifluoro ethane (2.25); 1,2-dibromo 1- chloro 2,2-difluoro ethane (2.23); 2,2-dibromo 1,1,1-trifluoro ethane (2.22); 1,2-dibromo 1,1-difluoro ethane (2.22); l-chloro 1,1,2-trifiuoro 2-iodo ethane (2.18); 1,1dibromo tetrafluoro ethane (2.15); 1,2-dibromo tetrafluoro ethane (2.14); and the like, and mixtures thereof.

The above listed specific gravities are for the most part determined at 25 C. If the process of the present invention is operated at other temperatures, corresponding adjustment in the above values should usually be made.

Water, as may be present either in the ore or in admixture with the more dense process liquid, can usually be tolerated in an amount such that agglomeration, emulsification, or the like does not occur.

Solid ore materials which may be ground in accordance with the present invention are those which have at least two physically separable components, preferably of different specific gravities. As used in the present specification, the term ore means either a natural or synthetic mineral or mineral mixture from which useful substances admixed with earthy matter or other gangue material can be liberated by grinding.

The so-liberated mineral values can be separated from residual gangue and recovered by techniques known to one skilled in the art. Sink-float and other gravity separation procedures, centrifugal, electrostatic, magnetic and the like processes are illustrative of suitable recovery and separatory methods which can be used.

A better understanding of the subject matter claimed may be obtained in light of the following examples which are set forth to illustrate and are not to be construed to limit the present invention.

Example 1 A number of runs were made grinding separate samples of a spodumene ore containing about 35 weight percent spodumene (Li O-Al O -4SiO having a specific gravity of about 3.1 and about weight percent free silica (specific gravity about 2.7) in the presence of process liquids of different densities. In these tests the ore samples were ground in a six inch laborator ball mill for a period of 5 minutes employing 1.1 kilogram of 1 inch by /1 inch ceramic cylinders as the grinding medium and about milliliters of the liquid. Each sample contained about 100 grams of ore previously ground to pass a 10 mesh screen (US. Standard Sieve size). After grinding, each sample was screened to determine the degree of grinding and the percent of the spodumene liberated was determined by sink-float separation employing CHBr CHBr (specific gravity 2.96) as the separating liquid, the liberated spodumene being recovered in the sink phase. A control run using water as a replace- 3 ment for the process liquid Was also included in this study.

The results of four runs employing different organic process liquids and water are summarized in Table 1.

TABLE 1 Process Liquid Ground Product Run (mesh) Spodumene No. Recovered,

percent Composition Specific +28 1 .28 1

gravity 1. 92 50. 1 49. 9 8S. 9 2. 50 57.1 42. 9 88.1 CHEM-(3111311.... 2 96 61.2 38 8 95.0 water (control). 35. 85 64. 15 67. 2

1 U.S. Standard Sieve.

These results clearly indicate that high liberation of the desired spodumene from the ore with less particle size reduction radially is achieved by the present novel process.

Example 2 In substantially the method set forth in Example 1, the solid mineral ores such as sylvite, feldspar, ilmenite, rutile, fluorite and the like may be ground while obtaining substantially the same advantages of valuable mineral liberation with minimum particle size reduction by employing as the process liquid at least one halogenated hydrocarbon liquid selected from the group consisting of methylene bromide, methylene chlorobromide, dibromo chloro methane, tribromo fluoro methane, bromo trichloro methane, bromo iodo methane, dibromo dichloro methane, bromo dichloro methane, 1,2-dibromo ethane, 1,1,2,2,- tetrafluoro 1,2-diiodo ethane, 1,1-dibromo 2,2-difluoro ethane, 1,2-dibromo 1,1,2-trichloro ethane, 1,2-dibromo Z-chloro 1,l,2-trifluoro ethane, 1,2-dibromo l-chloro 2,2- difluoro ethane, 2,2-dibromo 1,1,1-trifluoro ethane, 1,2- dibromo 1,1-difluoro ethane, l-chloro 1,1,2-trifiuoro 2- iodo ethane, 1,1-dibromo tetrafluoro ethane, 1,2-dibromo tetrafluoro ethane, and the like, and mixtures thereof, said grinding liquid having a specific gravity at operational temperatures greater than 1.0.

Various modifications may be made in the present invention without departing from the spirit or scope there- 'of, and it is to be understood that 1 limit myself only as defined in the appended claims.

I claim:

1. A method of grinding mineral ores to liberate mineral values therefrom which comprises grinding a mineral ore with at least one organic liquid compound having a specific gravity at operational temperatures greater than 1.0 thereby to liberate the mineral values from said ore.

2. The method of claim 1 wherein said organic liquid is inert and has a specific gravity at operational temperature, greater than 1.0 and up to about the specific gravity of the densest component of the solid material to be ground.

3. The method of claim 1 wherein said organic liquid has a specific gravity, at operational temperature, of from about 1.4 to about 3.0.

4. The method of claim 1 wherein said organic liquid compounds are selected from the group consisting of carbon tetrachloride; perchl-oroethylene; methylene bromide; methylene chlorobr-omide; dibromo chloro methane; tribromo fluoro methane; bromo trichloro methane; bromo iodo methane; dibromo dichloro methane; bromo dichloro methane; 1,2-dibromo ethane; 1,l,2,2- tetrafluoro 1,2-diiodo ethane; 1,1-dibromo 2,2'difluoro ethane; 1,2-dibromo 1,1,2-trichloro ethane; 1,2-dibromo 2- chl-oro 1,1,2-trifiuoro ethane; 1,2-dibromo l-chloro 2,2- difluoro ethane; 2,2-dibromo 1,1,l-trifluoro ethane; 1,2- dibromo 1,1-difluoro ethane; l-chloro 1,1,2-trifiuoro 2- iodo ethane; 1,1-dibromo tetrafluoro ethane; 1,2-dibromo tetrafluoro ethane; and mixtures thereof.

5. The method of claim 1 wherein said mineral ore is an ore containing spodumene and free silica.

No references cited.

0 WILLIAM W. DYER, JR., Primary Examiner.

G. A. DOST, Assistant Examiner. 

1. A METHOD OF GRINDING MINERAL ORES TO LIBERATE MINERAL VALUES THEREFROM WHICH COMPRISES GRINDING A MINERAL ORE WITH AT LEAST ONE ORGANIC LIQUID COMPOUND HAVING A SPECIFIC GRAVITY AT OPERATIONAL TEMPERATURES GREATER THAN 1.0 THEREBY TO LIBERATE THE MINERAL VALUES FROM SAID ORE. 